SCIENCE-GOSSIP. 



tree on one of these little worlds would have no 

 terrors, it would perhaps take ten minutes for you 

 to sink down to the earth, and when at last you 

 did reach the ground, instead of coming there with 

 a terrible momentum, you would come to rest as 

 gently as if you were lying down on a bed of 



swandown. There are many mysteries in this 

 universe of which at present we know next to 

 nothing, and among these mysteries is the nature 

 of the life, if life there be, on these beautiful little 

 worlds that partake, as our Earth does, of the 

 benefits dispensed by our great luminary, the Sun. 

 Observatory, Cambridge. 



ON THE OPISTHOSTOMiE OF BORNEO. 



By Edgar Albert Smith, F.Z.S. 



" \ \ 7HO has not admired the beauty of shells? 

 the rich lustre of the Cowries ; the glossy 

 polish of the Olives ; the brilliant painting of the 

 Cones ; the varied layers of the Cameos ; the 

 exquisite nacre of Mother-of- Pearl ? " Thus wrote 

 the late P. P. Carpenter some thirty-three years 

 ago. Had he known the wonderful shells, since 

 discovered, which form the subject of the present 

 notice, he would doubtless have included them in 

 his category of marvellous and beautiful forms. 



These remarkable structures belong to Opis- 

 thostoma, a group of very small operculate land- 

 shells, the type of which, and a few other species, 

 occur in India and adjacent localities. 



Until within the last six or seven years, only a 

 single form had been recorded from Borneo, but at 

 the present time as many as ten different kinds 

 have been described. This considerable increase 

 in the number of known species is almost entirely 

 due to the energy of Mr. A. Everett, who has done 

 so much to extend our knowledge of the fauna of 

 Borneo and the neighbouring islands. They have 

 only been found, at present, in the northern parts, 

 the rest of the island not having been carefully 

 searched by a competent collector. They occur on 

 limestone rocks in damp places, living apparently 

 upon the microscopic vegetation investing the 

 surface. 



Land-shells, as a rule, are not remarkable for 

 any very prominent ornamentation of the surface, 

 either in the form of spines, plications, or " varices," 

 such as obtain among the marine Gastropods. 

 Their beauty lies rather in the marvellous variety 

 of their form and colouration. We find the 

 exterior in the majority of cases more or less 

 even. True, among the Glausilia, which inhabit 

 most parts of the world, and the Strophice of the 

 West Indies, many species exhibit longitudinal 

 riblets (technically known as costaj, costulae, and 

 plica?) of considerable strength and thickness, and 

 in a fairly large number of Helicida similar 

 ornamention is also met with. Acroptychia metdbleta, 



indigenous to Madagascar, and a discovery of 

 recent years, is perhaps the most notable of all 

 the operculate land-shells on account of the 

 succession of beautiful longitudinal frill-like 

 lamellae which adorn the last or body- whorl. 

 This is practically an unique exception among the 

 Operculata of prominent longitudinal " sculpture." 

 Many species, it is true, have very beautiful frill- 

 like expanded "peristomes" to the aperture, but 

 are otherwise ornamented with mere striation or 

 cancellation. On the other hand, many species of 

 land-shells, both operculate and non-operculate, 

 exhibit strongly-marked spiral ridges or carinas. 

 These are especially well-developed in some of the 

 species of Cyclostomatida of Madagascar. 



Few species of land molluscs, however, exhibit 

 thorny processes of any importance. In Cylindrclla 

 elliotti and Choanopoma liystrix, from Cuba, and 

 Helicina stellata, and one or two other species, 

 ornamentation of a more or less spine-like character 

 is observable. On the contrary, among the marine 

 Gastropods and bivalved shells, spiny or prickle- 

 like "sculpture " is not uncommon. This kind of 

 ornamentation culminates, perhaps, among the 

 Muricidce. The "comb-shell," Murex tenuispina 

 and its allies may be mentioned as striking examples. 

 The genera Ranclla, Sistriim, Tudiatla, Pterocera, 

 Rostcllaria, Onustus, Astralium, Impcrator, Guildfordia 

 and Dclphinula also include some of the most spiny 

 of all the marine Gastropods. With the exception of 

 the thorny Oysters (SponJylits), and the Pinnas, and 

 a few cases among the Veneridcs, the Cockles 

 (Cardilda), and the Ckamida, the marine bivalves 

 do not afford many instances of spine-like sculpture. 

 Freshwater shells, like the terrestrial forms, are, as 

 a rule, devoid of spines. Still, there are some 

 exceptions, among which may be instanced a few 

 species of Melanin, the genus Io generally, a few 

 Neretina, notably N. longispina from the Mauritius, 

 and finally Tiphobia horei from Lake Tanganyika, 

 one of the most remarkable and interesting dis- 

 coveries of recent years among freshwater mollusca. 



